The proposed study will expand and continue an existing rural, community based cohort in Rakai District, southwestern Uganda. Project goals are to obtain descriptive epidemiological data on HIV-1 prevalence, annual seroconversion rates, patterns of transmission (including sexual and perinatal), progression to clinical disease, cofactors and coinfections, and behavioral risk factors. Knowledge, attitudes and behaviors (KAB) will be examined over time to evaluate the effects of health education and condom distribution programs. Increased access to STD treatment for the population of the district will also be implemented. As new barrier methods, therapies, and immunizations become available and are adequately tested, they may be incorporated into the project, contingent on approval by Ugandan authorities. In a preliminary study, all residents (adults and children) in 840 households in 21 randomly selected cluster (9 roadside trading center, and 12 rural villages) were enumerated. KAB and serological data were collected on all consenting residents. Serologic results on the 1133 consenting adults in the first 18 clusters indicate that, overall, 19.2% were HIV positive (34% in the roadside stratum, 11% in the rural stratum). Women aged 20 to 24 had the highest prevalence (52%). The pregnancy rate among HIV positive and HIV negative was 12%. Current or previous symptoms of genital ulcer disease (GUD) and STD, and number of reported sexual partners were associated with serostatus. Knowledge of condoms was low and use was below 2%. It is proposed that the project population be doubled to approximately 6800 in order to increase the power for statistical analysis of epidemiologic parameters and effects of preventive interventions (seroconversion, vertical transmission, risk factors, knowledge and behaviors) and that follow up be extended for 4 additional years. Scope of work will include annual KAB/serologic and health surveys, a vertical transmission study with 6-monthly follow up, social science research (indepth interviews and focus groups) and evaluation of preventive strategies (health education, condom distribution, referral for treatment of STDs).